MUSCLES ENGAGED Shoulders The shoulder is the most movable joint in the body. However, it is an unstable joint because of the range of motion allowed. This instability increases the likelihood of joint injury, often leading to a degenerative process in which tissues break down and no longer function well. Equipment Used Dumbbells The dumbbell, a type of free weight, is a piece of equipment used in weight training. It can be used individually or in pairs (one for each hand). Dumbbells vary in weight from 3lbs. up to 150lbs. Exercise Instructions Step 1 Starting from a seated position, holding the dumbbells up at 90 degrees just above your shoulders. Step 2 Press both dumbbells up above your head while fully extending your arms at the top of the motion. Step 3 Return the dumbbells to the starting position just above your shoulders and repeat for the recommended number of repetitions.